Core B, Reagent Development, will provide key reagents and resources for all program projects, including peptide epitopes, aliquots of donor PBMC samples, and HLA class II tetramers. The core will also provide HLA typing services, necessary to allow the appropriate matching of reagents and donor samples. Centralized production of these reagents and services will eliminate generation of redundant resources, and realize significant cost savings to each project. Furthermore, the use of reagents from a common core ensures uniformity across projects, facilitating cross study comparisons. The peptides and HLA class 11 tetramers produced by this core are necessary for each of the program's projects. More specifically, all of the projects will utilize peptide epitopes for assays requiring antigenic stimulation. Further, peptides are necessary for the generation of HLA class 11 tetramers. Tetramers in turn will be utilized by all projects as a way to enumerate and further characterize specific allergen T cells. In addition to these reagents, the core will process and distribute donor PBMC samples provided by the clinical research core (Core D), and perform HLA typing services for all clinical samples. Processing and distribution of donor PBMC samples is a key element of the Program, as functional analysis of PBMC is at the very essence of the activity of each individual Project. Determlnation of donor HLA type is useful for interpreting response patterns, and crucial for the generation of appropriate HLA class II tetramers. We have extensive experience all in activities associated with this core, as we have performed similar activities in support of previous contracts in the context of allergy studies, but also in infectious disease and cancer settings. Tetramers will be produced by the group of Dr. William Kwok, the leader in the generation and study of HLA class II tetramers. Taken together, the reagents and services provided by this core are integral to all of the program's projects and goals. The proposed work is also innovative as it provides a comprehensive set of reagents for studying epitopes and allergic responses in the context of common allergens and HLA class 11 molecules representative of most common allelic variants.